The present invention relates to fuel injection control apparatuses for an internal combustion engine having an injection control section for controlling a fuel injection mode of a direct injector and that of an intake passage injector.
Conventionally, an engine having an intake passage injector for injecting fuel into an intake passage and a direct injector for injecting fuel directly into a combustion chamber is known (for example, refer to Japanese Laid-Open Patent Publication No. 5-231221). In this engine, the air intake efficiency is improved by, for example, performing fuel injection through the intake passage injector while lowering the temperature in the combustion chamber using the heat of vaporization of the fuel injected by the direct injector.
Also, a vaporized fuel processing unit (for example, Japanese Laid-Open Patent Publication No. 10-231758) is known. The unit includes a fuel adsorption mechanism that adsorbs vaporized fuel produced in a fuel supply system, such as an engine fuel tank. The adsorbed fuel is purged into the intake passage at appropriate timings.
If the aforementioned purging by the vaporized fuel process unit is carried out in the engine having the intake passage injector and the direct injector, the following problem may occur.
More specifically, the fuel injected by the direct injector tends to be distributed in a non-uniform manner in the combustion chamber. That is, for example, the fuel may be distributed relatively dense in the vicinity of a spark plug but relatively scarce in the remaining portion of the combustion chamber. However, the fuel injected by the intake passage injector is vaporized sufficiently before being eventually supplied to the combustion chamber, as compared to the fuel injected by the direct injector. The fuel distribution in this case thus tends to become relatively uniform, as compared to the case of the fuel injected by the direct injector. In other words, in the aforementioned engine, the fuel injected by the direct injector and the fuel injected by the intake passage injector are distributed in the combustion chamber in different manners.
If purging is performed in this engine, it can be assumed that the influence of the purging on the combustion state of the engine may also differ depending on which of the injectors is operated. However, the problem has not been addressed to adequately and an improved fuel injection control apparatus has yet to be developed.